The present invention relates to a method of and an apparatus for recording an image, and more particularly to a method of and an apparatus for thermally recording an image, characters, or the like on a heat sensitive material with a thermal head, such that an area of the heat sensitive material other than the area in which the image or the like is thermally recorded in response to an input signal is thermally recorded at a predetermined density level.
Various new medical image diagnostic apparatus such as ultrasonic imaging apparatus, X-ray computerized tomographic apparatus, and nuclear magnetic resonance imaging apparatus have recently been widely used in addition to conventional X-ray photographic apparatus in the medical field. In such medical image diagnostic apparatus, an ultrasonic beam or X ray is applied to the body of a patient, and any change in the ultrasonic or X-ray energy that has passed through or been reflected from the patient's body is detected. Based on the detected change, image information of a localized region in the patient's body is produced. The image information is then displayed on a CRT, for example. A multiformat camera is used to record the image displayed on the CRT on a photosensitive material such as a silver-salt film through an optical system.
Subsequently, the film with such images recorded thereon are usually observed on a light table such as an illuminating box by a doctor who then diagnoses the imaged region based on the image information.
As shown in FIG. 1 of the accompanying drawings, when a film 2 is observed on a light table, the intensity of light which passes through a non-image frame area 6. of the film 2 is quite large as compared with an image area 4 of the film 2, making it difficult for the doctor to view the image area 4 which contains necessary information. In order to eliminate this drawback, there has been proposed an image recording apparatus which employs a scanning light beam, as disclosed in Japanese Laid-Open Patent Publication No. 60-224376 or 60-245365. According to the disclosed image recording apparatus, a non-image area of a film other than an image area thereof is blackened to a predetermined density level by being scanned by a light beam.
Since the proposed image recording apparatus employs a mechanism for scanning the light beam, the apparatus is large in overall size. Furthermore, the apparatus is expensive to manufacture as an optical system including a light deflector is highly costly, and the apparatus is not easy to use as the adjustment of the optical system is time-consuming. After an image has been recorded as a latent image on a silver-salt film in the disclosed image recording apparatus, the image has to be developed into a visible image which must then be fixed to the film. If a film with images fixed thereto is to be produced from the image recording apparatus, an automatic developing machine needs to be combined with the image recording apparatus. Therefore, an entire system including the image recording apparatus and the automatic developing machine is considerably large in size.
Heat sensitive recording processes employing heat sensitive materials for thermally recording images thereon are finding wide use in facsimile receivers and printers since the processes are easy to perform, the apparatus used are simple in structure and inexpensive to manufacture.
Heretofore, a transparent heat sensitive material is used in a heat sensitive recording process. More specifically, the transparent heat sensitive material is placed in intimate contact with an original, and light is applied to the heat sensitive material. The image area of the original then absorbs infrared radiation, which increases the temperature of the image area to enable the heat sensitive material to develop a color. The heat sensitive material however does not have a heat sensitivity which is high enough for the thermal head in a facsimile receiver to thermally record an image on the heat sensitive material. Another conventional heat sensitive material which can thermally record an image with a thermal head includes a heat sensitive layer which is not transparent. Therefore, even if such an opaque heat sensitive layer is coated on a transparent support, the resulting heat sensitive material does not have a desired degree of transparency.
Under the circumstances, there has been a demand for a transparent heat sensitive material on which an image can directly be recorded by a thermal head, so that the developed image on the heat sensitive material can be viewed on a light table or an overhead projector.
To meet such a demand, a heat sensitive material has been developed as disclosed in Japanese Patent Application 62-88197 filed by the applicant. The disclosed heat sensitive material has a heat sensitive layer coated on a support and having microcapsules containing at least a color former and a color developer. According to a first feature of the heat sensitive material, the color former comprises a colorless or a light colored electron donating dye precursor. After at least the color developer has been dissolved in in an organic solvent which is slightly soluble or insoluble in water, a coating agent comprising an emulsified dispersion and the microcapsules is prepared, and then coated and dried on the support. According to a second feature, the organic solvent in which the color developer is dissolved is ester. According to a third feature, the support comprises a transparent film. The heat sensitive material thus formed has a transparent heat sensitive layer which has high heat sensitivity. By coating the heat sensitive material on a transparent support, there is obtained a transparent heat sensitive material which is easily capable of producing a color using a thermal head.